Film feed mechanism in a motion-picture camera

ABSTRACT

A film mechanism for a motion-picture camera is provided. The film feed mechanism has a transport grip having a transport grip clip and at least one transport grip tip which engages in a sprocket hole of a motion-picture film that is transported at a predefinable film transport speed by the kinematics of the transport grip. The transport grip tip displaces the motion-picture film in an intermittent manner and runs through a closed trajectory whose reversing points determine the length of travel during the film transport. The kinematics of the transport grip can be dynamically and/or statically modified in accordance with the film transport speed by a modification to the relative positions of the transport grip and grip drive connected in an articulated manner to the transport grip in such a way that a constantly correct length of travel during a film transport step of the transport grip is guaranteed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Phase patent application of InternationalApplication Number PCT/DE2003/001987, filed Jun. 11, 2003, which claimspriority of German patent Application Number 102 29 380.5, filed on Jun.26, 2002.

BACKGROUND OF THE INVENTION

The invention relates to a film feed mechanism in a motion picturecamera.

From DE 38 35 329 C1 a film feed mechanism is known in a motion picturecamera which comprises a transport grip and a transport gearing. Thetransport grip consists of a transport grip clip which has at one end atleast one transport grip tip which moves the motion film, which is to betransported and has a perforated edge, step by step past the exposurewindow. A center section of the transport grip clip is connected throughan articulated grip joint to a crank which has in its rotational axis adrive shaft which is coupled to a film transport motor. The end of thetransport grip clip opposite the transport grip tip is connected to aswing bar which can swivel about a swing axis and which is fitted with alocking grip which at the end of a film transport step owing to thecontra movement of the locking grip and transport grip projects into asprocket hole of the film perforation and secures the picture state ofthe motion film during exposure of the film picture.

The transport gear which is formed from the crank and the swing barmoves the transport grip so that the transport grip tip runs through anelongated curve which is closed per se and which at one end enters intothe film running face and at the other end leaves it again so that thedistance between the two reversing tips determines the length of travelof the transport grip and thus a film transport step.

In order to adapt the curved path of the transport grip tips and theengagement depth of the locking grip in the known film feed mechanismthe swing bar axis of the swing bar which determines the mutual movementof the locking grip and the transport grip as well as the effectivelength of the swing bar and crank can be changed.

So that the motion film is always positioned at the correct place forthe exposure of the film picture the transport grip must transport themotion film always exactly by the length of travel, i.e., the distancebetween the reversing points of the curved path which is described bythe transport grip tips must be constant. As the length of travel of thetransport grip tips changes, i.e. in the event of different length filmtransport steps not only does the distance of the exposed film pictureschange relative to each other but the tip of the locking grip projectinginto a corresponding sprocket hole of the moving film is no longer inexact alignment with the relevant sprocket hole and strikes an edge ofthe perforation and thereby damages the moving film.

Since considerable mass forces act on the transport grip tip at thereversing points of the curved path of the transport grip tip, this tipbends outwards at the reversing points in the sense of extending thecurved path, i.e. with an upper reversing tip upwards and with a lowerreversing tip downwards. This deformation of the transport grip tipresults in an extension of the length of travel so that the distancebetween the film images which are to be exposed is changed and the filmperforation is damaged through a locking grip which does not engageprecisely in a sprocket hole.

Since the deformation of the transport grip tips increases as thetransport speed of the film rises the length of travel also rises as thetransport speed of the film increases so that owing to the faultypositioning of the moving film the position of the locking grip deviatesmore and more from the site of the associated sprocket hole resulting inmore and more serious damage to the film.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a film feed mechanismof the type already mentioned which ensures a constantly correct lengthof travel with each film transport step of the transport grip over theentire picture frequency range.

The solution according to the invention ensures a constantly correctlength of travel of the transport grip over the entire picture frequencyrange and thus an exact mutual spacing between the film pictures whichare exposed and are to be exposed of the motion picture film camera. Bypositioning the moving film with precision it is ensured that in a filmfeed mechanism with a locking grip the locking grip tip projectsprecisely into a sprocket hole at all film transport speeds so thatdamage to the moving film is avoided.

The solution according to the invention is based on the idea ofcompensating the unavoidable deformation of the transport grip tipsresulting from the mass forces acting on same in dependence on the filmtransport speed and thus of producing and maintaining the predeterminedexact length of travel.

The kinematics of the transport grip can be dynamically changed as thefilm transport speed changes or can be statically altered when settingthe film transport speed. In a further variation the kinematics of thetransport grip can be statically preset with the target for the desiredfilm transport speed and can be combined with a dynamic regulationduring film transport and changing film transport speed.

One advantageous embodiment of the solution according to the inventionis characterised in that as the film transport speed rises the reversingpoints of the transport grip clip are moved towards each other. Bychanging the position of the transport grip clip it is possible withsimple means to influence the upper and lower reversing point of thetransport grip tip taking into account the mass forces which occur atthe reversing points and thus to ensure a correct length of travel forthe transport grip.

The kinematics of the transport grip are preferably changed by alteringthe relative position between the transport grip and a grip driveconnected for articulated movement with the transport grip.

Alternatively or in combination with the aforesaid change in thekinematics the kinematics of the transport grip can be changed byshifting the attachment of the end of the transport grip clip oppositethe transport grip tip on a control element which controls theprojecting movement of the transport grip and a locking grip projectinginto the film perforation at the end of a film transport step so thatthe locking grip releases the motion film again when the transport gripprojects again into the film perforation.

More particularly the attachment of the transport grip on the controlelement can be shifted towards the axis of the control element as thefilm transport speed increases.

Changing the kinematics of the transport grip through intervention inthe kinematics by adjusting suitable points of the kinematics can becarried out both electrically and mechanically.

An electrical adjustment of the kinematics of the transport grip iscaused by changing an actuating signal sent by a camera control to anelectrically actuated control member whereby the control member canconsist of a servo motor which is connected directly or indirectly tothe transport grip clip or the attachment on the control element. Inorder to change the kinematics of the transport grip the camera controlcan change the actuating signal continuously or discontinuously independence on the film transport speed.

A mechanical adjustment of the kinematics of the transport grip can takeplace by means of a mechanical control member connected to the gripdrive or to the transport grip and preferably consisting of acentrifugal force regulator.

An alternative to this exists where during adjustment of a filmtransport speed the position of the grip drive is moved in relation tothe transport grip or the connection between the grip drive and thetransport grip is changed.

BRIEF DESCRIPTION OF THE DRAWINGS

The idea on which the invention is based will now be explained infurther detail with reference to an embodiment illustrated in thedrawings.

FIG. 1 shows a diagrammatic view of a film feed mechanism with thecurved path of a transport grip;

FIG. 2 shows a diagrammatic view of a change in the kinematics of thetransport grip with different transport speeds through a displacement ofthe drive axis of a crank drive;

FIG. 3 shows a diagrammatic view of a change in the kinematics of thetransport grip with different transport speeds through shifting theconnection of the transport grip clip on a control element; and

FIG. 4 shows a diagrammatic view of an electrical change in thekinematics of the transport grip by means of a servo motor and aspeed-dependent actuating signal which is issued by the camera control.

DETAILED DESCRIPTION OF THE DRAWINGS

The film feed mechanism illustrated diagrammatically in FIG. 1 serves totransport a moving film 1 whose edge or edges is/are provided with aperforation (sprocket holes) 10. The film feed mechanism has at leastone transport grip 2 and at least one locking grip 3, i.e. either atransport and locking grip 2, 3 engaging in a perforation on one side,or two transport and locking grips 2, 3 which engage in perforations onboth sides. Furthermore the film feed contains a film drive with a driveshaft 6 which is connected to a film transport motor (not shown infurther detail), a crank 4 and a control element 5. The or eachtransport grip 2 and locking grip 3 is designed as a projecting grip andhas at ends facing the moving film 1 one or more transport grip tips 21or locking grip tips 31 which project alternately into the sprocketholes 10 of the moving film 1.

The at least one transport grip 2 has a transport grip clip 20 which atone end has a transport grip tip 21 and at the other end is connected toan attachment 24 on the control element 5 which swings or rotates abouta control element axis 50. A center section of the transport grip clip20 is connected through a grip joint 22 to a first crank arm 41 of thecrank 4 which is connected through a crank joint 43 to a second crankarm 42 which is attached to the drive shaft 6.

The at least one locking grip 3 includes a locking grip pin 30 which hasat one end the locking grip tip 31 and at the other end is connectedthrough a locking grip clip 33 to a locking grip lever 32 which isattached through an attachment 34 to the control element 5.

The movement of the transport grip 2 during a film transport step iscomposed in accordance with the kinematics of the transport grip 2described above of a horizontal movement and a vertical movement so thatduring transport of the moving film 1 the transport grip tip 21describes the curved path B diagrammatically illustrated in FIG. 1. Byconnecting the transport grip clip 20 and the locking grip lever 32 atdifferent connecting points 24, 34 on the control element 5 a mutualhorizontal movement of the transport grip tip 21 and locking grip tip 31is generated so that during a film transport step in which the movingfilm 1 is moved on by one film picture, the locking grip tip 31 islocated outside of the film plane whilst the transport grip 21 isprojected into the film sprocket 10 and moves the film 1 according tothe predetermined length of travel L between an upper reversing point P1and a lower reversing point P2.

At the end of a film transport step the transport grip 21 leaves thefilm sprocket 10 and the locking grip tip 31 projects into a sprockethole 10 which is aligned with the locking grip tip 31 thereby ensuring afixed picture state of the moving film 1 from which the part to beexposed is positioned in front of the picture window which is releasedduring exposure of the film 1 through an aperture mounted in front ofthe picture window.

FIG. 1 shows the transport grip 2 in the two end positions when thetransport grip tip 21 is located in the reversing points P1 and P2, andshows the locking grip 3 during projection of the locking grip tip 31into the film perforation 10 or after leaving the film plane.

The pre-requirement for a correct picture state, i.e. a constantdistance between two successive film pictures to be exposed is an exactobservance of the length of travel L of the transport grip 2 between theupper reversing point P1 and the lower reversing point P2 of the curvedpath B. If the film feed mechanism is provided like the film feedmechanism illustrated in FIG. 1 with a locking grip 3, which need notnecessarily be provided, then it is also necessary to observe the exactlength of travel L equally also for a smooth handling of the moving film1 so that the locking grip tip 31 projects into a sprocket hole 10 whichis flush with same and does not owing to a faulty positioning of themoving film 1 strike the edge of a sprocket hole 10 or even a film webbetween two sprocket holes 10. A faulty positioning of the moving film 1through the transport grip 2 would thus lead to considerable damage tothe moving film 1.

The decisive feature for maintaining the exact length of travel L is theexact geometric positioning of the transport grip tip 21 at the upperand lower reversing points P1, P2. As a result of mass forces however adeformation of the transport grip tip 21 which is dependent on the filmtransport speed occurs at the reversing points P1 and P2 which leads tothe transport grip tip 21 being bent upwards at the upper reversingpoint P1 and downwards at the lower reversing point P2. This deformationof the transport grip tip 21 as a result of mass forces results in anextension of the length of travel L as the film transport speedincreases.

In order to ensure that particularly even with higher film transportspeeds the correct length of travel L of the transport grip tip 21 isobserved, according to the subject of the present invention anintervention is made in the kinematics of the transport grip 2 independence on the film transport speed so that the transport grip tip 21exactly observes the upper and lower reversing point P1 and P2respectively taking into account the mass forces which appear.

A change in the kinematics of the transport grip 2 can basically takeplace in many different ways. It is essential that the vertical motioncomponents of the transport grip clip 20 is reduced as the filmtransport speed rises so that taking into account the mass forcesengaging on the transport grip tip 21 and the resulting deformation ofthe transport grip tip 21 the position of the upper and lower reversingpoints P1, P2 of the transport grip tip 21 is observed.

FIG. 2 shows a first possibility of compensating the extension of thelength of travel L caused by the deformation of the transport grip tip21, i.e. of counteracting a change in the film transport step caused bythe deformation of the transport grip tip 21.

By extending the drive shaft 6 from position (point) A with slow filmtransport speed to position (point) A′ with faster film transport speeda corresponding change is produced in the kinematics of the transportgrip 2 which is shown in dotted lines in FIG. 2. Through this change inthe kinematics an upper reversing point G1 of the articulated grip joint22 is moved according to G1′ and a lower reversing point G2 of thearticulated grip joint 22 is moved according to G2′ so that at higherfilm transport speeds the reversing points G1 and G2 of the articulatedgrip joint 22 are moved relative to each other.

An alternative to this form of compensation of a deformation of thetransport grip tip 21 at higher film transport speeds is a change in thelength of the crank arm so that similar to the illustration according toFIG. 2 a displacement of the upper and lower reversing points G1 and G2of the grip joint 22 is caused.

FIG. 3 shows a second variation of compensating the extension in thelength of travel L caused by the deformation of the transport grip tip21, i.e. of counteracting a change of film transport step caused by thedeformation of the transport grip tip 21.

In this embodiment the kinematics of the transport grip 2 are changed bya shift in the attachment 24 of the end of the transport grip clip 20opposite the transport grip tip 21 on the control element 5 in that forexample as the film transport speed increases the attachment 24 to thecontrol element axis 50 is moved, i.e. from point K (reversing point) topoint (reversing point) K′. In the case of the upper reversing point P1of the transport grip tip 21 the attachment 24 is thus located at pointK1′, whilst it is located in the case of the lower reversing point P2 atpoint K2′.

Both variations can also be combined with each other, i.e. a shift inthe articulated grip joint 22 is linked with a shift in the attachment24.

The shift in the drive shaft 6 from position A to position A′ as well asof the attachment from point K to point K′ illustrated in FIGS. 2 and 3can take place both electrically and mechanically.

One possibility of moving the points A and K mechanically lies inconnecting the switch for adjusting the film transport speedmechanically to a slider which moves the film drive during a change inthe film transport speed so that there is the desired change illustratedin FIG. 2 of the kinematics of the transport grip 2. Empiricallydetermined values can thereby be taken into consideration so that with acorresponding rise in the film transport speed the exact length oftravel L of the transport grip 2 is observed.

An alternative embodiment consists in connecting the film drive to acentrifugal force regulator which in dependence on the film transportspeed generates a continuous or stepped change in the position of thepoint A according to FIG. 2 and thus an approach of the reversing pointsG1 and G2 of the grip joint 22 as well as a continuous or stepped changein the position of point K according to FIG. 3 and thus a displacementof the reversing points K1 and K2 of the attachment of the transportgrip clip 20.

FIG. 4 shows diagrammatically an electrical displacement of the positionof the drive shaft 6 which is mounted together with the film transportmotor (not shown) on a plate 7 which is connected to a servo motor 8through an adjusting spindle 70. An actuation of the servo motor 8causes a displacement of the plate 7 in the direction of the doublearrow S according to FIG. 4 so that the drive shaft 6 and thus thecentre of the crank 4 moves into a position dependent on the filmtransport speed for approaching the reversing points G1 and G2 of thegrip joint 22.

For this purpose the servo motor 8 is connected to a camera control 9which sends an electrical actuating signal to the servo motor 8 whichdepends on the adjusted film transport speed. This actuating signal canbe sent steplessly for each desired film transport speed from the cameracontrol 9 to the servo motor 8. Alternatively a discontinuous change inthe position of the plate 7 takes place in dependence on fixedpredetermined film transport speeds. Possibly, and with the arrangementdiagrammatically illustrated in FIG. 4, a continuous change can also becarried out in the kinematics of the transport grip 2 in dependence on acontinuously changing film transport speed by way of example forproducing special picture effects so that also in this type of use anexact picture state as well as a smooth handling of the moving film 1are ensured.

Alternatively or additionally this adjustment can also take placerelative to the attachment 24 of the transport grip clip 20 on thecontrol element 5 in that for example the attachment 24 is connected toa cam plate whose alignment is influenced by means of the servo motor 8.

1. A film feed mechanism in a motion picture camera with at least onetransport grip which, has a transport grip clip and at least onetransport grip tip which through the kinematics of the transport grip,projects into the perforation of a motion picture film which is to betransported at a predeterminable film transport speed, moves the motionpicture film intermittently, and runs through an elongated curved pathwhich is closed and whose reversing points determine the stroke lengthof travel during the transport of the film, wherein the kinematics ofthe transport grip is changeable in dependence on the film transportspeed and wherein the kinematics of the transport grip, is changeable byaltering the relative position between the transport grip and a gripdrive which is connected for articulated movement to the transport grip.2. A film feed mechanism according to claim 1 wherein the grip drivecomprises a drive shaft which is connected to a film transport motor anda crank which connects the drive shaft to an articulated grip joint ofthe transport grip clip, wherein a position of the drive shaft ischangeable in relation to the articulated grip joint.
 3. A film feedmechanism according to claim 2 wherein as the film transport speedrises, reversing points of the articulated grip joint, which connectsthe transport grip clip of the transport grip to the crank, are movedtowards each other.
 4. A film feed mechanism in a motion picture camerawith at least one transport grip which, has a transport grip clip and atleast one transport grip tip which through kinematics of the transportgrip projects into a perforation of a motion picture film which is to betransported at a predeterminable film transport speed, moves the motionpicture film intermittently, and runs through an elongated curved pathwhich is closed and whose reversing points determine the stroke lengthof travel during the transport of the film, wherein the kinematics ofthe transport grip are changeable in dependence on the film transportspeed and wherein the kinematics of the transport grip is changeable byshifting an attachment of an end of the transport grip clip opposite thetransport grip tip on a control element, wherein the control elementcontrols the projection movement of the transport grip and at least onelocking grip which projects into the film sprocket at the end of a filmtransport step so that the locking grip releases the film when thetransport grip projects once more into the film sprocket.
 5. A film feedmechanism according to claim 4 wherein the attachment of the transportgrip on the control element is moved relative to the axis of the controlelement as the film transport speed increases.
 6. A film feed mechanismaccording to claim 4 wherein the control member can pivot about acontrol element axis, and wherein the attachment of the transport gripclip and an attachment of a locking grip lever, arranged on either sideof a control member axis, control the transport grip tip of thetransport grip and a locking grip tip of the locking grip through thecontrol member.
 7. A film feed mechanism according to claim 6 whereinthe control member is formed by arms rotating about the control elementaxis with the attachments of the transport grip clip and locking griplever.
 8. A film feed mechanism according to claim 6 wherein the controlmember is formed by a disc with the attachments of the transport gripclip and locking grip lever.
 9. A film feed mechanism in a motionpicture camera with at least one transport grip which, has a transportgrip clip and at least one transport grip tip which through kinematicsof the transport grip projects into a perforation of a motion picturefilm which is to be transported at a predeterminable film transportspeed, moves the motion picture film intermittently, and runs through anelongated curved path which is closed and whose reversing pointsdetermine the stroke length of travel during the transport of the film,wherein the kinematics of the transport grip are changeable independence on the film transport speed and wherein the kinematics of thetransport grip is changeable by means of an actuating signal sent bymeans of a camera control to an electrically actuated control memberwhich is connected to at least one of a grip drive, the transport gripand an attachment.
 10. A film feed mechanism according to claim 9wherein the control member consists of a servo motor connected directlyto the transport grip clip.
 11. A film feed mechanism according to claim9 wherein the camera control changes the actuating signal continuouslyin dependence on the film transport speed.
 12. A film feed mechanismaccording to claim 9 wherein the control member consists of a servomotor connected indirectly to the transport grip clip.
 13. A film feedmechanism according to claim 9 wherein the camera control changes theactuating signal discontinuously in dependence on the film transportspeed.
 14. A film feed mechanism in a motion picture camera with atleast one transport grip which, has a transport grip clip and at leastone transport grip tip which through kinematics of the transport gripprojects into a perforation of a motion picture film which is to betransported at a predeterminable film transport speed, moves the motionpicture film intermittently, and runs through an elongated curved pathwhich is closed and whose reversing points determine the stroke lengthof travel during the transport of the film, wherein the kinematics ofthe transport grip are changeable in dependence on the film transportspeed, wherein the kinematics of the transport grip is changeable bymeans of a mechanical control member connected to at least one of a gripdrive, the transport grip and an attachment, and wherein the mechanicalcontrol member comprises a centrifugal force regulator.